• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.411-415
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• 2004

In this paper, a double artificial neural network (ANN) approach and the efficient machining database building scheme are presented for the prediction of surface roughness in high-speed machining. In this approach, 4 machining parameters and used for the prediction of cutting force components, and the combinations of 4 parameters and the predicted cutting force components are finally used for the prediction of surface roughness. The experimental results comparing the these results with the predicted values using simple 4 input nodes have been also investigated to verify the effectiveness of the proposed approach.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.7
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• pp.1123-1130
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• 2017

This paper deals with the dynamic surface control based tracking control for a drone equipped with a 2-DOF manipulator. First, the dynamics of drone and 2-DOF manipulator are derived separately. And we obtain the combined model of a drone equipped with a manipulator considering the inertia and the reactive torque generated by a manipulator. Second, a dynamic surface control based attitude and altitude control method is presented. Also, multiple sliding mode control based position control method is presented. The system stability and convergence of tracking errors are proven using Lyapunov stability theory. Finally, the simulation results are given to verify the effectiveness of the proposed control method.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.334-338
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• 2001

In order to investigate the effects of various injection hole shapes on the film cooling of turbine blade, three test models having cylindrical and shaped holes were used. A three-dimensional Navier-Stokes code with standard k-$\epsilon$ model was used to compute the film cooling coefficient on the film cooled turbine blade. Over 330,000 grids were used to compute the flow over the blade. Mainstream Reynolds number based on the cylinder diameter was $7.1{\times}10^4$. The turbulence intensity kept at $5.0\%$ for all inlets. The effect of coolant blowing ratio was studied for various blowing ratios. For each blowing ratios, wall temperatures around the surface of test model were calculated. Temperature was visualized using cartesian cut-cell method to obtain traces of the injected secondary air on the test surface, so we could interpret the film effectiveness as temperature distributions.

• Journal of Biosystems Engineering
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• v.14 no.4
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• pp.262-271
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• 1989

Red pepper is one of the most important agricultural products in Korea. Generally, raw red pepper is dried after harvest and the dried red pepper is powdered. Washing process is necessary to produce clean powder before powdering process. This study, therefore, was performed to analyze the drying characteristics of the rewetted red pepper and the energy utility during hot-air-convective and infrared-radiant drying. Drying effectiveness, De, was defined for the analysis of energy utility in this study, and its value was determined according to the energy source. Infrared-radiant drying was more favorable than convective drying according to drying effectiveness. But the temperature variation was appeared between the radiant surface and opposite surface of red pepper in infrared-radiant drying.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.139-146
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• 2005

We selected six kinds of stretching exercises that can be easily acquired and put to practical use by back pain patients and arranged the practicing order of the exercising method after measuring the % MlVC of the muscle power when a normal person was exercising with a surface EMG. Among the patients complaining of back pain, 20 case groups were given the selected exercise and physical therapy, and 20 control groups were only given a physical therapy. Before and 2 weeks, 4weeks, 6 weeks and 8 weeks after the exercise therapy, a muscle power was measured with a fitness machine and the effectiveness of the exercise was compared. After six weeks difference of the muscle power between the case group and control group was shown, and after 8weeks the case group manifested the stronger muscle power than that of the control group in both male and female. Exercising therapy clearly seems to be helpful in strengthening the muscle power of the back pain patients.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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• pp.9-16
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• 2021

Modern combat has been extended to the concept of real-time response to a variety of threats simultaneously occurring in vast areas. In order to quick command determination and accurate engagement in these threats, the combat system has emerged in frigate. Frigates conduct anti-surface, anti-submarine, and anti-aircraft as the core forces of the fleet. In this study, the combat effectiveness measures naval frigates using AHP (analytic hierarchy process) method. A hierarchical structure for measuring the combat effectiveness was developed, and weights of criteria were calculated by expert surveys and pair-wise comparisons. In addition, the combat effectiveness of frigates was synthesized and compared. The weights for each attribute were calculated, and the weights for the three main attributes were in the order of act (0.594), evaluate (0.277), and see (0.129). As a result of calculating the weight, anti surface warfare (0.203) was the highest. The combat effectiveness of FFG Batch-III, which has advanced hardware and software and improved combat system capabilities, see (1.73 to 2.56 times), evaluate (1.68 to 2.08 times), and act (1.31 to 3.80 times) better than the comparative frigate. In summarizing the combat effects of the frigate, FFG Batch-III was 1.41~2.95 times superior to the comparative frigate. In particular, a group of experts evaluated the act importantly, resulting in better combat effectiveness.

• Tribology and Lubricants
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• v.31 no.4
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• pp.157-162
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• 2015

In this study, an ultrasonic nanocrystalline surface modification (UNSM) technique is applied to tungsten carbide-cobalt (WC-Co) to extend the service life of carbide parts used in press mold. The UNSM technique modifies the structure, reduces the surface roughness, increases the surface hardness, induces the compressive residual stress, and increases the wear resistance of materials by introducing severe plastic deformation. The surface roughness, hardness, and compressive residual stress of WC after UNSM treatment improve by about 42, 10, and 71%, respectively. A wear test under dry conditions is used to assess the effectiveness of the UNSM technique on the friction and wear behavior of WC. The UNSM technique is found to reduce the WC friction coefficient by approximately 21% and enhance the wear resistance by approximately 85%. The improved friction and wear behavior of WC may be mainly attributed to the increased hardness and compressive residual stress. Moreover, the WC specimen is treated by UNSM technique using three different WC, silicon nitride (Si₃N₄) and stainless steel (STS304) balls. The surface treated by WC balls shows the highest hardness when compared with treatment by stainless steel and silicon nitride balls. According to the obtained results, the UNSM technique is believed to increase the durability of the carbide component by improving the friction and wear behavior.

• Transactions of Materials Processing
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• v.19 no.4
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• pp.224-229
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• 2010

During the multi-pass wire drawing process, wires suffer a great amount of plastic deformation that is through the cross-section. This generates tensile residual stress at surface of drawn wires. The generated residual stress on surface is one of the problems for quality of wires so that prediction and reduction of residual stresses is important to avoid unexpected fracture. Therefore, in this study, the effect of process variables such as semi-die angle, bearing length and reduction ratio on the residual stress was evaluated through Finite Element Analysis. Based on the results of the Analysis, a prediction model was established for predicting residual stress on the surface of high carbon steel(AISI1072, AISI1082). To identify the effectiveness of the proposed model, X-ray diffraction is used to measure the residual stresses on the surface. As the result of the comparison between calculated residual stresses and measured residual stresses, the model could be used to predict residual stresses in cold drawn wire.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.255-261
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• 2008

The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the ground rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with Rainflow counting method. Also, Pamglen-Miner rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.100-108
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• 1999

rectangular open or in-filled trenches(concrete and rubber) are often used to reduce the ground vibrations caused by propagating surface(Rayleigh) waves. This paper presents the experimental data for estimating the vibration screening effectiveness of open or in-filled trenches Field dynamic tests using the exciter which can generate the 100kN vertical cyclic load in the range of 100-250 Hz were performed. One hundred and twenty accelerometers to measure the ground response are used in 6 radial direction. To compare the effectiveness of the vibration isolation the contours of the amplitude ratio with the dimensionless parameters dividing by Rayleight wave lengths were presented.